Grate-bar



(NoModeL) 2 Sheets-Sheet 1. W. U. PAIRBAIRN.

Grate Bar. No. 242,765; Patented June 14,1881.

PETERS. Pmwmha n w, Washington. D. c,

' (No Model.) 1 v 2 Sheets-Sheet 2.

W. U. FAIRBAIRN.

Grate Bar.

"No. 242,765. I Patented June 14, I881.

WITNESSES I INVENTUR r N. PETERS. Pholohihngmphw. Washington. 0.0.

UNITED STATES PATENT OFFICE.

WILLIAM U. FAIRBAIRN, OF HYDE PARK, MASSACHUSETTS.

GRATE-BAR.

SPECIFICATION forming part of Letters Patent No. 242,765, dated June 14, 1881.

Application filed August 7, 1880.

To all whom "it may concern:

Be it known that LWILLIAM U. FAIRBAIRN, of Hyde Park, in the county of Norfolk and State of Massachusetts, have invented a new and useful Improvement in Grate-Bars, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming a partof this specification, in explaining its nature, in Which- Figure 1 is a perspective of my improved grate-bar; Fig. 2, a vertical central section thereof; Figs. 3and 4, a cross-section; and Fig. 5 represents the arrangement of these gratebars in connection with the fire-box and ashpit of a steam-boiler furnace as I have always used'them.

It is very essential, in order to maintain uniform combustion in a furnace, to as nearly as possible supply the fuel with a uniform and sufficient quantity of oxygen or air well distributed beneath it; and in furnaces'as ordinarily constructed, having parallel gratc-bars extending from the front backwardly, the air is taken up very largely by the front section of the fire, and the back part of the fire, or the part more remote from the draft, suffers in consequence, and an unequal combustion of the fuel and a consequent loss in the amount of heat developed therefrom result.

My invention is designed toprovidethe rear or back section of the fuel with sufficient air to maintain a combustion equal to that of the front by introducing air thereto through a chamber or passage in each of the g-ratebars; and in constructing my grate-bars to accomplish this purpose I also am enabled to make a lighter and stronger bar from the same amount of metal, and to keep the bar cool enough to prevent its wearing, twisting, or warping from the influence of the heat.

A is the bar. It has a passage, a, in the web to, extending from the opening 61?, at or near the front end of the bar, to the side opening or openings, a at or near its rear, whereby the air may be introduced into the combustionchamber at its rear portion, or at such points as may be necessary to secure full combustion of the fuel. The web a and the fire-supportin g surface a are kept cool enough by the passage of the air through the grate-bar to prevent injury from heat. Any suitable form of firesupporting surface may be given the grate- (No model.)

bar. The passage through the grate-bar preferably is formed by coring in the casting.

It will be observed that the lateral openings a are arranged at or near the rear end of the bar, and I so locate them in order that the current of air may pass through a greater portion of the length of the bar and make its exit at or near the rear of the combustion-chamber,

where fresh air is most needed. That portion of the fire supported by the front portion of the bar receives sufficient air from between the bars to properly support combustion.

The openings a at the front end of the bar are so arranged as to take air from the ashpit, these bars being shown of the ordinary form to rest upon a ledge inside of the ash-pit,

which ledgeopractically is the dividing-linebetween the ash-pit and fire-box.

The passage a, which extends from the openin g a located at the front portion of the ashpit, conveys the air through the hollow bar to the rear of the fire, and there delivers it between the bars as air heated by convection and containing its full supply of oxygen, while air rising between the bars from the ash-pit chamber is only heated by radiation-a much less efficientmethod-andis apt tobe deprived of a part of its oxygen. In addition to this, there is such a draftthrough the heated bar that the delivery of the heated air at the rear of the fire, directly between the grate -bars, produces at that point, mingling with the products of combustion from the front part of the fire, a sort of blow-pipe flame, and produces much more perfect and intense combustion.

Perfect con1bustion-th at is to say, the combu'stion of carbon to carbonic acid-gives six thermal units of heat with a given amount of 0 oxygen. Imperfect combustion, or the combustion of carbon to carbonic oxide, gives only four thermal units of heat for an equal amount of oxygen, while the combustion of carbonic oxide to carbonic acid with an equal amount of oxygen will give eight thermal units.

In the use of heated air instead of air at ordinary temperatures, the tendency to burn coal to carbonic oxide instead of carbonic acid is very much diminished, and the amount of unconsumed oxygen which is heated by the fuel and escapes uncombined at the head of the stack is also reduced. These things were demonstrated by the late McInorn Rankin in a series of experiments published about fourteen years ago in Les Mondes and I here present an efficient and simple means of using the blow-pipe flame with heated air at the back of the fire, and at a point where it can be delivered upon the surface to be heated-such as a boiler-with its greatest efficiency.

I am aware that hollow grate-bars are no new.

Hollow grate-bars have been heretofore used to conductair from the ash-pit, orfrom thefront of the furn ace outside the ash-pit, to the bridgewall, illustrations of which construction are shown in English Patents Nos. 1,023 of 1855 to Milton, 2,868 of 1868 to Jones and others, 1,685"

of 1856 to Seymour, and 2,942 of 1860 to Stevens. This last patentee also employs these hollow bars to conduct air through the bridgewall to a point high up over the fire, and a similar contrivance was suggested in Daviss provisional specification No. 2,597 of 1854.

Hollow grate-bars have also been used to conduct airfrorn the exterior and front of the ash-pit to the rear part of the ash-pit, where it is delivered into the ash-pit downward, creating a sort of eddy, and forms substantially the whole supply of air for the fire. This is shown in English Patent No. 2,091 of 1877 to Moore. They have also been used to conduct forced blasts of air from the exterior of the furnace into the spaces between the gratebars, and also lifting blasts for slack into the fire. Illustrations of these constructions are shown in the American patents to Williams, No. 211,074, ofDecember, 1878, and N0.164,729, to Gregg, June 22, 1875.

A grate-bar channeled on the under side and having perforations in the channel-wall is shown in the Hill patent, No. 51,455, December 12, 1865.

The English patent to Wicks, N 0. 2,397 of 1857, has a hollow grate-bar open at the front end, and which is arranged to project past the rear wall of the ash-pit. It has a ledge on top of the bar, about over this rear wall, to keep the coal and ashes from passing beyond the ash-pit wall, and back of this ledge the hollow of the bar opens up through the upper surface of the bar; but my bar has no ledge, and the hollow channel does not open on the upper surface of the bar, but on the sides, and is thus simpler and easier kept in order. The reason forthe Wicks construction is given, that by the mingling of hot air through the bars and cold air at this place under the bars the fire of a bakers oven may be handled, and when he strikes down the combustion by introducing cold air he has flues to prevent the smoke and sulphur-fumes from entering the oven.

English Patent No. 3,061 of 1807 also shows a hollow bar; but it is so constructed that normally the hollow would not have a draft through it, but would be stopped up, either by the brick-work against which it abuts or by mortar. To avoid the destruction of the bar from this cause, small holes are pierced at each end in opposite sides to admit air; but they are not so arranged as to get any efficiency in a blow-pipe action delivering air at the rear of the fire in quantity for combustion.

So that I say these sorts of grate-bars are not like my invention. The air for combustion is taken with my grate-bar in the usual way through the ash-pit. It rises in the usual way through the spaces left between the grate-bars but, besides this, my grate-bars are hollow from end to end, and they have an opening into the cavity of the bar at the front end of the ashpit, and an opening high up on the sides of the bar at the rear end of the ash-pit. In this way the fresh air containing abundance of oxygen is taken into the front end of the gratebars and heated in its traverse, and then passes hetween the grate-bars on both sides into the fire at the rear end of the fire-box, and, rising through the fire, supplies heated oxygen at that'point in considerable quantities, and thereby increases combustion at the point where the supply of air is usually most likely to fail, and yet at the point where combustion, on account of the presence of heated combustible gases, can be made most rapid and most durable, and a long flame produced to enter upon its work of heating.

I claim as my invention and desire to secure by Letters Patent of the United States- A grate-bar provided with end supports and having a hollow web, the ends of which web are sloped inward and downward from the end supports, and the cavity of which web opens at its front end into the ash-pit, and at or near its rear closed end, through the sides of the web, into the interval between the bar and its next adjacent bar, constructed substantially as and for the purpose described.

WILLIAM U. FAIRBAIRN.

Witnesses:

THos. WM. CLARKE, A. J. OETTINGER. 

